The evolution of AlTiSi intermetallic phases in Ti-added A356 Al–Si alloy

Although there are reports in open literature on the formation and morphologies of AlTiSi particles in aluminum alloys, there is not much information on its growth mechanism or orientation relationship with the aluminum matrix. The flakes and blocks morphologies of AlTiSi intermetallics in foundry alloys is similar to that of Al3Ti. However, there is not any report to date to specify the favorite conditions under which either of these morphologies would prevail. This has technological bearing since the plate like morphology could grow to such extends to disturb or even hinder the flow of molten alloy within feeding channels.The application of optical, SEM and TEM in analysis of as-cast Ti-added A356 Al–Si alloy shown the formation of AlTiSi intermetallics with different morphologies and sizes. In addition, the two main morphologies of block and flake AlTiSi particles are originated from the fine needles and spherical particles form during the early stages of solidification. The orientation relationships between the intermetallic phases and Al matrix are also examined.

► Ti addition to A356 alloy forms flake and block AlTiSi intermetallics.
► Information given on the origin and growth mechanism of the flake and block.
► Information given on their crystallographic relationship with the Al matrix.
► Flakes/blocks has technological bearing on molten alloy flow in feeding channels.